The present invention relates to apparatus for installing a motion detector, lighting fixture or the like on a wall or ceiling.
An electrical fixture such as a lighting fixture is normally secured to a wall or ceiling by mounting it on a junction box which is itself secured to the framework of the wall or ceiling. Electrical wires for carrying the electrical power are routed through the walls or ceiling to the junction box where the ends of the wires are exposed for connection to the fixture. The junction box, which is required by standard building codes, opens out onto the wall or ceiling and provides a safe shielded enclosure for the electrical connections inside the box as well as a secure footing for supporting the weight of the fixture once it is mounted.
In a common procedure for installing an electrical fixture on a wall or ceiling a cross bar is attached across the open end of the junction box and supports the fixture. The cross bar is usually a flat metallic strip which is screwed into threaded lugs at the edges of the junction box. Attached to the cross bar is a central length of threaded pipe, which serves as a support post for the fixture, which may be secured to the central pipe with a bracket and nut, for example. In the installed configuration the cross bar supports the full weight of the fixture. In a common alternative procedure, fixtures are sometimes screwed directly to the junction box at the threaded lugs without using a cross bar. In either case, before the fixture can be attached to the cross bar or junction box, it must be electrically connected to the wires routed through the walls to the junction box. The electrical connections are normally made by splicing the wires together using specialized wire connectors designed for this purpose.
The difficulty in installation comes in supporting the fixture while the wires are being connected and while the fixture is being attached to the junction box. The first problem is in splicing the wires together. An installer needs a certain amount of working space to join the wires comfortably. If the fixture is attached loosely to the central support post on the cross bar, i.e., to the post that is intended to support the fixture, the space behind the fixture is generally too cramped for comfortable work. Installers typically want more space to work in. As a result, a typical installer will hold the fixture at the junction box by cradling or resting it on his or her arm while twisting the wires together with wire connectors. For ceiling installations this is done while perched on a ladder. Sometimes instead of cradling the fixture to support it, an installer will merely hold it by the electrical wires with several fingers of one hand while using the remaining fingers and the second hand to make the electrical connections. After the electrical connections are made, the fixture is sometimes left hanging by the newly connected wires while the installer gets the necessary hardware for mechanically attaching the fixture base to the junction box.
This procedure has a number of disadvantages. It is awkward for the installer to balance the fixture during the installation process, particularly while standing on a ladder. As a result it can take longer to install. To the professional installer slower installation means lower earnings. In addition, the awkwardness in installation sometimes causes an installer to drop a fixture with resulting damage to the fixture, which sometimes then has to be returned to the manufacturer. Furthermore, the electrical connections may be damaged when a fixture is left hanging from the wires. For a larger fixture, which may be heavier or more awkward, a second worker must sometimes hold the fixture while a first worker makes the electrical connections and secures the fixture to the cross bar or junction box. This has the obvious disadvantage that it requires two workers to install the fixture. Not only is this inconvenient for the home owner installing a fixture on his or her own, for the professional installer it is simply not cost-effective to use two workers for a task that should require only one.
There is an additional problem when installing devices known as passive infrared (PIR) motion detectors. A PIR motion detector is a device that turns on a light or activates an alarm when a person or other warm object such as an automobile enters the field of view of the device. The device includes a specially arranged array of lenses or mirrors that define the field of view of the device. The array of lenses or mirrors directs infrared energy from a person or object located in the field of view to a sensitive electronic detecting unit that senses the impinging infrared energy and triggers the light or alarm in response. Here there is a greater chance of damage to the device if it is dropped during installation or even if it is hung by the electrical connections in an intermediate stage of installation because PIR motion detectors are more susceptible to damage than an ordinary light fixture. Here the lenses or mirrors and detecting unit can become misaligned, and the electronics of the infrared sensing unit can be damaged. Once the alignment has been disturbed, it is then more difficult, and more time-consuming, to align the field of view of the unit after it is mounted on the wall or ceiling, assuming the unit has not been so damaged that it has become inoperative.
These installation problems, although seemingly minor, are widespread, and installers have come to accept them as an annoying but inevitable aspect of the job.